I. Field of the Invention
This invention relates to pozzolanic mixtures for the stabilization and disposal of landfill leachate.
II. Background of the Related Art
Landfill leachate contains toxic and other water soluble contaminants from residential and commercial waste disposal. Landfill leachate also contains non-aqueous contaminants suspended or mixed with the water soluble contaminants. Leachate can percolate through the subsoil of the landfill and contaminate the water supply of surrounding communities.
Kiln dust is a fine powdery waste product often derived from the manufacture of portland cement in cement kilns. Kiln dust is difficult to handle at disposal facilities and can not be reused in wet process cement processing plants.
The solid wastes collected from residential and commercial sources can be used as fuel in power boilers or incinerators. The burning of this waste produces fly ash, a fine airborne particulate commonly collected from the product of the combustion stream using smoke stack scrubbers with electrostatic precipitators, baghouses and other conventional smoke stack scrubbing operations. Often fly ash may contain a certain amount of excess lime which is added during the dry scrubbing process. The burning of waste also leaves a solid residue in the form of granular, random-size free flowing bottom ash, which remains in the bottom of the incinerators or power boilers after combustion is complete.
Both bottom ash and fly ash contain toxic metals and other materials which by themselves present environmental and health hazards. Fly ash typically contains lead, chromium and cadmium, along with other hazardous metals. Bottom ash often contains lead, ferrous metals, chromium and cadmium. Typically, landfill leachate contains various organic compounds, biological contaminants, suspended petroleum products, mercury, and other hazardous metals.
The non-metallic components in bottom ash are suitable for use as a lightweight aggregate substitute in making concrete and like products in the construction industry. Thus, there are significant economic advantages to be derived from the recovery of the granular bottom ash materials from the incineration residue. In addition, the non-metallic recoverables of bottom ash can be used to dilute the environmentally hazardous fly ash for disposal in landfill operations. Methods for recovery of useful materials from refuse bottom ash are disclosed in U.S. Pat. No. 4,669,397, the contents of which are incorporated herein by reference.
U.S. Pat. Nos. 4,274,880 and 4,226,630 disclose means for disposing of hazardous liquid wastes in combination with fly ash. Neither of these references discloses or suggests the use of kiln dust, fly ash and the optional inclusion of bottom ash for the disposal of hazardous liquids. In addition, neither of these patents disclose or suggest that such a cementitious mixture may be combined to dispose of landfill leachate Specifically, U.S. Pat. No. 4,226,630 is directed towards the disposal of water-borne heavy metal sludge produced in metal processing and refining plants, by combining the sludge with a very specific type of fly ash formed through the combustion of sub-bituminous coal which is only mined in the "Powder River Basin" of Gillette, Wyoming.
U.S. Pat. No. 4,375,986 discloses the combination of waste water which has a pH not greater than 2, fly ash, and lime (Ca(OH).sub.2), Portland cement, "ground blast furnace slag", or slag cement. However, it does not disclose nor suggest the novel combination of landfill leachate, fly ash and kiln dust to form a pozzolanic mixture
U.S. Pat. No. 4,028,130 is directed towards the disposal of digested sewage sludge by combining it with lime or its equivalent of lime dust or cement kiln dust, with fly ash and sufficient water. The disposal of landfill leachate is nowhere taught nor suggested in U.S. Pat. No. 4,028,130.
U.S. Pat. No. 4,101,332 reissued as Re 30,943 is directed towards a mixture of fly ash, cement kiln dust and water to produce a durable mass which is capable of supporting surfacing as pavement bases. There is no disclosure or suggestion in this patent for using any of these components to stabilize landfill leachate. U.S. Pat. No. 4,018,617, which was based on the same application as Re 30,943 is directed towards a mixture of fly ash or a pozzolan (to the exclusion of lime), cement kiln dust and aggregate to produce a hard, strong, durable mass for pavement-like surfacing. The disclosure does not suggest the use of such a mixture for stabilizing landfill leachate and requires a large proportion of aggregate.
U.S. Pat. No. 4,038,095 is also based on the same patent application as Re 30,943, but is directed toward a mixture or method for making a mixture for pavement bases and the like utilizing fly ash, lime stack dust and aggregate. It does not, however, disclose the use of this mixture for the stabilization of landfill leachate.
Lastly, U.S. Pat. No. 4,432,800 is directed towards the treatment of kiln dust used in pozzolanic reactions with calcium oxide, calcium hydroxide or sodium hydroxide. The treated kiln dust is used with a pozzolan such as fly ash and a filler to produce a durable mass. There is no disclosure or suggestion in U.S. Pat. No. 4,432,800 for using such a mixture for the stabilization of landfill leachate. Nor is the optional use of bottom ash disclosed.
Accordingly, the related art does not hitherto disclose or suggest any mixture or method useful for the stabilization and disposal of landfill leachate.
It is an object of this invention to provide a method and pozzolanic mixture which chemically converts to a strong, hard and durable mass with favorable handling and leaching characteristics.
Another object of this invention is to permanently stabilize hazardous materials contained in landfill leachate, as well as similarly stabilize the other hazardous components of the fly ash, kiln dust and bottom ash mixture.